i regret__that i'm unable to help youa.sayingb.to sayc.say

i regret__that i'm unable to help youa.sayingb.to sayc.say
i regret__that i'm unable to help you
a.saying
b.to say
c.say

i regret__that i'm unable to help youa.sayingb.to sayc.say
B
regret to do 对要做的事遗憾